Evaluation of laboratory tests used in screening ambulatory patients

Multiple other tests have been suggested for screening healthy patients. Hopefully, the above illustrations give a perspective with regards to the incidence of disease versus other causes that would lead to abnormal test results. The most frequent cause of an abnormal test result is physiologic variation, laboratory variation, or both. Even in laboratories with excellent quality assurance programs, the results falling outside the reference ranges most likely indicate physiologic variation, laboratory variation, or both. The physician will obtain more meaningful data from the laboratory when testing is ordered to confirm diagnostic suspicions that were raised during the history and physical examination of the patient. When a physician receives abnormal test results that were ordered as screening tests without any diagnostic suspicion, a search should be made for signs and symptoms that would correlate with that abnormal test. In the absence of any evidence that would indicate underlying disease, it would usually be unnecessary to pursue follow-up testing.